QMenu: Submenu partially hidden by main menu

Issue:
When a submenu is displayed by a customContextMenuRequested signal, the top part of the submenu is covered by the main menu and gets invisible.

How to reproduce the issue:
1. Run the attached example code
2. Request the customContextMenu (Windows : Right click on the window, Android/iOS : Long press on the window)
3. The top part of the submenu is covered by the main menu and gets invisible. (See attached screenshot_20240603.png)

• This issue is reproduced with following Qt version and platform :
    Qt 6.5.5 + iOS 15
    Qt 6.5.5 + iOS 17.4.1.
    Qt 6.6.3 + iOS 17.4.1.
    Qt 6.7.1 + iOS 17.4.1.

• This issue is not reproduced on Widows, Mac, nor Android.